Recirculation unit



United States Patent [72] inventors Rudolph M. Pnulson 217-29, 50 Ave., 11364; Roy A. Watt, 3359, 210th, Bayslde, New York 11361 [21 Appl. No. 872,532

(22] Filed Oct. 30, 1969 [45] Patented Dec.l,l970

[54] RECIRCULATION UNIT 10 Claims, 2 Drawing Figs.

[52] US. Cl 165/22, l65/50 [5 l] Int. Cl F24! 3/00 [50] Field ofSearch...............,..........H............ l65/22,50

[56] References Cited UNITED STATES PATENTS 2,984,460 5/l96l Gardner et al 165/50 Primary Examiner-Charles Sukalo Artorney-Pennie, Edmonds, Morton, Taylor and Adams JUUL lllllll Patented Dec. 1, 1910 v \s 5%. *i

FT I

FIG. 2

; l l 5 s I O INVENTORS RUDOLPH M. PAULSON BY ROY A. WATT 'M, M JW ATTORNEYS RECIRCULATION UNIT BACKGROUND OF THE INVENTION Conventional water distribution systems used in dwelling houses and other buildings generally include a hot and cold water supply line each of which has a number of branch lines leading to hot and cold water outlet fixtures, respectively. Both the hot water supply and the cold water supply line are usually dead ended at some convenient point beyond the most remote hot and cold water fixtures. With such a system, it will be readily recognized that where there is no consumption of water from the hot water outlet fixtures for an extended period of time, or, when water is drawn from the hot water outlet fixtures only intermittently, a rather lengthy waiting period must be endured before hot water at the desired temperature is actually forthcoming from the fixture. This condition is due to the fact that the temperature of the water within the hot water supply line is materially lowered by heat losses therefrom with the result that the consumer must wait for a considerable period of time before the cold water from the hot water supply line is flushed out through the open outlet fixtures by a fresh supply of water at the desired temperature. Besides being highly annoying, such delays are costly since a relatively large volume of lukewarm, but otherwise usable. water is lost through the drainage facilities of the particular system while waiting for the issuance of usable hot water.

In recent years, several attempts have been made to correct the above-described situation. However, none of the proposed solutions have been entirely satisfactory. For instance, in one known construction, an auxiliary return pipe leading from the most remote hot water fixture back to the hot water supply tank is provided. Due to the difference in the specific gravities of the hot water issuing from the hot water supply tank and the cooled water being returned through the auxiliary pipe, a gravitational flow is effected which acts to return the cooled water back to the hot water supply tank where it can be reheated and subsequently redistributed into the hot water supply line. However, from a practical standpoint such a system presents significant drawbacks. First of all, because of the additional pipe required, the installation cost is rather high and in some cases prohibitive. Moreover, if the hot water outlet fixtures are located on the same level, as is often the case in one story manufacturing plants an and one level dwelling houses, such a system will not operate at all, or be very sluggish in operation. For these reasons, among others, such a system has not been found to provide a practical solution to the problem discussed above.

In another known construction, there is provided a continuous hot water loop extending past each of the hot water fixtures and back to a central hot water source. This system is quite complex in construction and relatively expensive to operate since it requires a circulating pump in the hot water loop that must be operated continuously and a series of hot and cold water mixing valves for keeping the temperature of the water in the loop constant. In addition, the system employing such a hot water loop is entirely unsuitable for use in presently existing structures since the installation of such a system cannot be accomplished without excessively expensive alterations in the existing hot and cold water distributing system.

With the above observations in mind, it is the principal object of the present invention to provide an automatically controlled recirculation unit adapted for easy connection between conventional hot and cold water supply lines and which, in operation, substantially reduces the waiting period before hot water issues from the hot water outlet fixture.

SUMMARY OF THE INVENTION In accordance with the teachings of the present invention. there is provided an automatically controlled recirculation unit for maintaining a relatively constant supply of water at a predetermined minimum temperature at outlet fixtures spaced along the hot water supply of a conventional hot and cold water distribution system. Moreover, the recirculation unit is one which is compact in size, simple and economical to produce, easy to install, dependable and inexpensive to operate. In construction, the recirculation unit includes a flow pipe connected between the hot and cold water supply lines to form a closed flow path therebetween. The flow pipe contains a pump which acts to selectively circulate water in the hot water line which has cooled to a temperature below the desired distribution temperature from the hot water supply line into the cold water supply line. The pump is automatically activated by a control means responsive to the temperature of the water in the hot water supply line. The control means includes, more particularly, a temperature controller which constantly monitors the temperature in the hot water supply line and activates the pump automatically when that temperature falls below the desired distribution temperature.

In order to prevent the leakage of water from the high temperature side of the unit to the low temperature side of the unit when the pump is idle, an automatic check valve controlled by the temperature controller is provided. This valve is positioned downstream of the pump and remains in a closed position when the pump is idle, however, the check valve is opened simultaneously with the activation of the pump to permit free flow of cooled hot water into the cold water supply line.

In order to cool the recirculated water before entrance into the cold water supply line, cooling means controlled by the temperature controller and activated simultaneously with activation of the pump is located downstream of the pump and upstream of the check valve. The cooling means insures that the temperature of the water in the cold water supply line is not materially disturbed by the influx of generally higher temperature water during the pumping operation. The function of the cooling coils is augmented by the inclusion of means for regulating the rate of flow through the cooling means. This means acts to insure that the cooling means operates at maximum efficiency so that water returned to the cold water supply line is fully cooled,

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a diagrammatic view of a conventional hot and cold water distribution system employing the recirculation unit of this invention.

FIG. 2 is a detailed view showing the internal parts of the recirculation unit of this invention.

DETAILED DESCRIPTION OF THE INVENTION As shown schematically in FIG. I, the recirculation unit of this invention can be used with a conventional hot and cold water distribution system. The distribution system includes a hot water supply line 1 and a cold water supply line 2 provided with branch lines 3 and 4 leading to hot and cold water outlet fixtures 3 and 4'. Both the hot and cold water supply lines are fed from a main water supply line 5 at substantially equal pressures. Water is delivered to the hot water supply line from a hot water supply 6 and water is supplied to the hot water heater from the main water supply line 5 by an inlet pipe 7.

In a distribution system of the type shown in FIG. I, heat losses from the hot water supply line, even though insulated, gradually effects a reduction in the temperature of the water initially supplied at any outlet fixture of the hot water us supply line. When the temperature of the water therein has fallen below the desired distribution temperature, it is advantageous to replace this cooled hot water with a fresh supply of heated water from the hot water source of supply 6. This avoids prolonged waiting periods before hot water at the desired distribution temperature is forthcoming at the outlet fixtures. These waiting periods would otherwise occur because of the time needed to permit the cooled hot water to be flushed out of the hot water supply line through the open outlet fixtures and replaced by a fresh supply from the hot water supply. Waiting periods of this nature are not only costly in terms of time but are also wasteful of otherwise usable water which, because of the waiting time, is lost through the drainage facilities of the particular system.

In recognition of the savings in time and money which would accrue from elimination of protracted waiting periods of the type described, the present invention provides a recirculation unit for maintaining a relatively constant supply of heated water at the desired distribution temperature in the hot water supply line. The recirculation unit operates to circulate cooled hot water in the hot water supply line into the cold water supply line and eventually back into the hot water heater and storage tank where it may be reheated and sub sequently redelivered to the hot water supply line for consumption at a later time.

The recirculation unit, indicated diagrammatically by reference numeral 8, is adapted to be readily connected between the hot and cold water supply lines to form a closed recirculation loop therebetween. As shown in FIG. 1, the recirculation unit is connected to the hot and cold water supply lines downstream of the hot and cold water outlet fixtures; however, it is to be understood that it may be placed at other points along the hot and cold water supply lines. In general, the proper location of the recirculation unit is determined by such factors as the relative frequency of consumption from the various outlet fixtures, the layout of this particular hot and cold water distribution system with which the unit is intended for use, etc; it being the primary object to locate the unit so as to obtain a balanced recirculating flow of water through the system.

Referring to FIG. 2, it will be seen that the recirculation unit includes a flow pipe connected between the hot and cold water supply lines to form a closed flow path therebetween. The flow pipe 10 is connected to the hot and cold water supply lines by standard pipe fittings 11 and 12 respectively. The standard pipe fittings 11 and 12 each are equipped with a manual shutoff valve 11' and 12'. These valves permit the recirculation unit to be isolated from the rest of the system for general maintenance purposes.

The How pipe 10 contains a pump 9 which acts to selective ly circulate cooled hot water standing in the hot water supply line into the cold water supply line. The pump is a simple impeller type pump of conventional construction and it is driven by a conventional alternating current motor 15. The pump is activated whenever the temperature of the water standing in the hot water supply line falls below the desired distribution temperature.

To eliminate the need for manual surveilance of the water temperature in the hot water supply line for determining when the pump should be activated, the temperature of the water in the hot water supply line is continuously monitored and provision is made to automatically activate the pump when this temperature has fallen below the desired distribution temperature. For this purpose, control means responsive to the water temperature in the hot water supply line is provided. This means includes a spirit plug 16 which is projected into the flow pipe 10 at a point upstream of the pump 9 and downstream of the point of connection with the hot water supply line. The spirit plug is sensitive to the temperature of the water in the hot water supply line and a reading of that temperature is transmitted to a temperature controller 17 via an interconnecting capillary tube 18 which communicates with the spirit plug through a pressure tight nut in the flow pipe 10. The pressure of the gas trapped in the capillary tube varies in accordance with the temperature senses by the spirit plug. The temperature controller 17 contains a pressure sensitive cutoff switch 17' which is activated by the pressure of the gas in the capillary tube and operates to turn on and turn off power to the motor 15. With this arrangement, the temperature controller may be preset to the pressure corresponding to the desired distribution temperature and thereafter the pump will be automatically activated when the pressure of the gas in the capillary tube falls below this value.

in order to prevent the possibility of obtaining inaccurate readings of the temperature of the water in the hot water supply line, the flow pipe 10 is, by preference, provided with suitable insulation 13 similar to the insulation [3 normally surrounding the hot water supply line I. The insulation 13 extends advantageously at least up to a point located downstream of the spirit plug 16 and, preferably, up to a point located immediately upstream of the pump 9. With this arrangement, the rate of heat loss from the flow pipe on the hot water side of the recirculation unit in the vicinity of the spirit plug 16 conforms substantially to rate of heat loss from hot water supply line 1. Thus the temperature of the water in the hot water side of the recirculation unit, especially, in the critical area surrounding the spirit plug [6, accurately reflects the temperature of the water in the hot water supply line at all times.

During periods when the pump is operating it becomes important to insure that the temperature of the water in the cold water supply line is not materially disturbed by the influx of higher temperature water from the hot water supply line. in order to cool the recirculation water so that this condition will not occur, the recirculated water is pumped through cooling coils 14 positioned downstream of the pump. An electric fan 18 is positioned so that when activated it will direct a flow of cool air over the cooling coils 14. The fan is connected electrically via lead cables 23 to the temperature controller 17 and is activated thereby simultaneously with the activation of the pump in the same manner described above in connection with activation of the pump.

To insure that water recirculated through the unit is fully cooled before entering the cold water supply line, means for regulating the rate of flow through the cooling coils is provided. This means includes a bypass duct 20 connected across the inlet and outlet sides of the pump 9. The bypass duct includes a primary flow control valve 21 which cooperates with a secondary flow control valve 22 which is positioned immediately downstream of the point of connection between the bypass duct 20 and the outlet side of the pump 9. Both the primary and secondary flow control valves 21 and 22 may be operated manually and may be relatively adjusted to obtain the most efficient rate of flow through the cooling coils.

During periods when the pump is idle (when the water temperature in the hot water supply line is equal to or greater than the desired distribution temperature), leakage of hot water from the hot water side of the unit through the pump and into the cooling coils and cold water supply line beyond may occur. Such leakage generally occurs at a time when the cold water outlet fixtures 3 are opened while the hot water outlet fixtures 4 remained closed thereby causing a frictional pressure drop in the cold water supply line 2 and thus permitting undesirable leakage of hot water there into. Although this leakage is slow and would not normally be of any significance, it is avoided by the inclusion of a cold water supply line entrance valve 24. This valve is positioned downstream of the cooling coils at a point slightly upstream of the point of connection between the flow pipe 10 and the cold water supply line 2. This valve is electrically operated by the temperature controller and is connected thereto by electrical lead cables 25. When the pump is idle, the entrance valve is in a closed position to prevent infusion of hot water into the cold water supply line. However, when the temperature controller energizes the pump and the electrical fan, the entrance valve is also energized causing it to open so that the circulated water can flow through it and into the cold water supply line.

The operation of the recirculation unit is described as follows. The distribution temperature at which hot water is to issue from the hot water outlet fixtures is first determined. The temperature controller 17 is then set to the pressure corresponding to that temperature.

Assuming first that the water temperature in the hot water supply line is at least equal to the desired temperature, the entire system will remain at equilibrium with the pump and electrical fan idle and the entrance valve in a closed position. In

the event it is desired to withdraw hot water, one or more of the hot water outlet fixtures is simply opened. The withdrawn water will be automatically replaced with a fresh supply of heated water from the hot water source of supply. It will be noticed that if frequent consumption of hot water is contemplated there will be no need to activate the recirculation unit; and, in fact, the recirculation unit will not be activated during periods of frequent consumption.

Assuming, however, that water has been left standing in the hot water supply line for a considerable length of time without consumption, heat losses radiating from the hot water supply line will eventually cause the temperature of the water standing therein to fall below the desired distribution temperature. This reduction in temperature will be continuously sensed by the spirit plug 16 and a corresponding reduction in the pressure of the gas in the capillary tube 18 will occur. When the pressure of the gas in the capillary tube falls below the pressure corresponding to the desired distribution temperature, the electrical pressure switch 17 in the temperature controller 17 will be closed, in turn, supplying power to the pump motor and the electrical fan 19 and thereby activating the same and opening the entrance valve 24.

The cooled hot water in the hot water supply line is now pumped through the recirculation unit in the direction of the arrows in FIG. 2. This water is pumped through the recirculation unit at a pressure equal to the static pressure of the water in the hot water supply line plus the pressure increment imparted to the recirculating water by the action of the pump. Since the static water pressure in the hot water supply line is substantially equal to the static water pressure in the cold water supply line, the pressure at which water is being pumped will be slightly greater than the static pressure of water in the cold water supply line. This differential in pressure during operation of the pump is sufficient to create a reverse flow in the direction of dotted arrow 26in the cold water supply line.

As the cooled hot water is withdrawn from the hot water supply line and recirculated into the cold water supply line, it will be replaced by a fresh supply of hot water from the central hot water supply, 6. Eventually, the temperature of the water in the hot water supply line will again attain the desired distribution temperature. This condition is sensed by the spirit plug which, in turn, causes a corresponding increase in the pressure of the gas in the communicating capillary tube. When this pressure has again reached the pressure corresponding to the desired distribution temperature, the cutoff switch in the temperature controller is opened to shut off the supply of power to the pump and to the electric fan and to close the entrance valve in the process. The recirculation unit remains idle until the water temperature in the hot water supply line has again fallen below the distribution temperature at which time this cycle is repeated as described above.

With a hot and cold water distribution system employing the recirculation unit of the present invention several advantages, in addition to those already mentioned, are presented. First of all, the pump which is used will only have to operate against very little pressure and move a low volume of water since the water pressure differential between the inlet and outlet sides of the pump will be quite small. Therefore, the pump need only supply sufficient power to overcome the frictional resistance of water flowing through the various conduits of the recirculation unit and the main hot and cold water supply lines; and thus it may be made advantageously quite small in size requiring a low electric input, say for example, as little as one-fifteenth of an ampere.

The low power requirements of the various components generally means that their physical size is also quite small. Thus, the recirculation unit can be housed as a compact unit in no more space than required for a conventional dehumidifer or window air conditioning unit. In addition, the recirculation unit of this invention is exceedingly easy to install since it requires only two simple connections to the existing hot and cold water supply lines of the conventional hot and cold water distribution system. Another important advantage obtained by LII the use of the recirculation unit of this invention is that with such a unit usable water is not lost through the drainage facili ties of the system while waiting for lukewarm water to be flushed and replaced by a fresh supply of hot water at the desired distribution temperature.

The above description of the present invention has been made with reference to the preferred embodiment, however, it is to be understood that the changes may be made thereto without departing from the scope of the invention as set forth in the following claims.

We claim:

I. In a hot and cold water distribution system having a hot water supply line, a cold water supply line, outlet fixtures spaced along the hot water supply line, means for supplying cold water to the cold water supply line. means for supplying hot water at a temperature higher than a predetermined value to the hot water supply line; the improvement comprising an automatically controlled recirculation unit for maintaining a relatively constant supply of water in the hot water supply line for consumption from the outlet fixtures at a temperature at least equal to said predetermined value, said recirculation unit comprising:

a. a flow pipe connected between the hot and cold water supply line to form a flow path therebetween;

b. a pump in the flow pipe for circulating water which has cooled below said predetermined value through the flow pipe from the hot water supply line to the cold water supply line; and

c. control means operatively connected to the pump for activating the pump when the temperature of the water in the hot water supply line has fallen below said predetermined value.

2. The apparatus according to claim 1 further comprising:

a. cooling means in the flow pipe downstream of the pump for cooling the circulating water as it passes through the flow pipe.

3. The apparatus according to claim 1 further comprising:

a. a cold water supply line entrance valve in the flow pipe downstream of the pump, said valve being normally closed to prevent infusion of hot water from the hot water supply line into the cold water supply line when the pump is idle.

4. The apparatus according to claim 3 wherein: a. said control means is operatively connected to said pump and valve for simultaneously activating the pump and opening the valve.

5. The apparatus according to claim 4 further comprising: a. flow regulating means for regulating the rate of flow through the cooling means.

6. The apparatus according to claim 5 wherein said flow regulating means includes:

a. a bypass duct connected across the inlet and outlet side of the pump;

b. a first flow control valve in the bypass duct; and

c. a second flow control valve in the flow pipe downstream of the point of connection between the bypass duct and the outlet side of the pump and upstream of the cooling means.

7. The apparatus according to claim 6 wherein the cooling means includes:

a. a series of cooling coils disposed in the inlet pipe downstream of the pump and upstream of the cold water supply line entrance valve; and

b. a fan positioned to direct a flow of air past the cooling coils.

8. The apparatus according to claim 7 wherein: a. said control means is operatively connected to the fan for simultaneously activating said fan with activation of the pump and opening the valve.

9. The apparatus according to claim 8 wherein said control means includes:

a. a temperature controller operable to supply power to the pump and cold water supply line entrance valve when subjected to a pressure corresponding to said predetermined temperature; and

between the hot water supply line and the flow pipe; and

b. a capillary tube connected between the spirit plug and the temperature controller, in fluid communication therewith, said capillary tube containing a gas the pressure of which varies in accordance with the temperature of the spirit plug.

g g UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 543 836 Dated December 1, 1970 Inventor(s) Rudolph lson It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 44, "an" should be deleted.

Column 2, line 64, "us" should be deleted.

Column 4, line 25, "18" should be changed to --l9--.

Column 4, line 49, "3" should be changed to 4'-.

Column 4, line 50, "4 should be changed to 3 Signed and sealed this 6th day or Jul 1971.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. WILLIAM E. SGHUYLER, JR.

Attasting Officer Commissioner of Patents 

